The objectives of this project are to elucidate biochemical mechanisms controlling the synthesis, storage, release, action and termination of action of norepinephrine in the adrenergic neurones and how to assess these in the intact animal. This year attention has focused 6-fluoronorepinephrine as a substitute transmitter for norepinephrine and on evaluation of functional aspects of Alpha-adrenoceptor function, intrajunctional (Alpha1-) and extrajunctional (Alpha2-) locations of Alpha-adrenoceptors have been further defined. A method has been developed to estimate the concentration of norepinephrine at Alpha1-adrenoceptors which regulate blood pressure responses in pithed rats and is being applied to studies of disposition of released norepinephrine and regulation of Alpha1- adrenoceptors.